For starters the RB2 doesn't have the O ring head like the models that preceded it, it has the parachute style that is also fitted to the Superstar/sport, if I remember correctly the Stutzen had the adjustable transfer port screw, which if it's fitted then you can wind out the grub screw and then be able to fit a softer spring, either get Tinbum to make you a tuning kit or contact Welsh Willy for the same, tuning it won't really add much value to it, from memory the trigger on the RB2 Stutzen was pretty nice.
Pete